diff --git a/hw/acpi/ich9.c b/hw/acpi/ich9.c
index 799351e..25bc023 100644
--- a/hw/acpi/ich9.c
+++ b/hw/acpi/ich9.c
@@ -94,7 +94,8 @@
     ICH9LPCPMRegs *pm = opaque;
     switch (addr) {
     case 0:
-        pm->smi_en = val;
+        pm->smi_en &= ~pm->smi_en_wmask;
+        pm->smi_en |= (val & pm->smi_en_wmask);
         break;
     }
 }
@@ -198,6 +199,7 @@
          * support SMM mode. */
         pm->smi_en |= ICH9_PMIO_SMI_EN_APMC_EN;
     }
+    pm->smi_en_wmask = ~0;
 
     acpi_update_sci(&pm->acpi_regs, pm->irq);
 }
diff --git a/hw/isa/lpc_ich9.c b/hw/isa/lpc_ich9.c
index 18718d7..71a9f7a 100644
--- a/hw/isa/lpc_ich9.c
+++ b/hw/isa/lpc_ich9.c
@@ -407,12 +407,28 @@
     }
 }
 
+/* config:GEN_PMCON* */
+static void
+ich9_lpc_pmcon_update(ICH9LPCState *lpc)
+{
+    uint16_t gen_pmcon_1 = pci_get_word(lpc->d.config + ICH9_LPC_GEN_PMCON_1);
+    uint16_t wmask;
+
+    if (gen_pmcon_1 & ICH9_LPC_GEN_PMCON_1_SMI_LOCK) {
+        wmask = pci_get_word(lpc->d.wmask + ICH9_LPC_GEN_PMCON_1);
+        wmask &= ~ICH9_LPC_GEN_PMCON_1_SMI_LOCK;
+        pci_set_word(lpc->d.wmask + ICH9_LPC_GEN_PMCON_1, wmask);
+        lpc->pm.smi_en_wmask &= ~1;
+    }
+}
+
 static int ich9_lpc_post_load(void *opaque, int version_id)
 {
     ICH9LPCState *lpc = opaque;
 
     ich9_lpc_pmbase_update(lpc);
     ich9_lpc_rcba_update(lpc, 0 /* disabled ICH9_LPC_RBCA_EN */);
+    ich9_lpc_pmcon_update(lpc);
     return 0;
 }
 
@@ -435,6 +451,9 @@
     if (ranges_overlap(addr, len, ICH9_LPC_PIRQE_ROUT, 4)) {
         pci_bus_fire_intx_routing_notifier(lpc->d.bus);
     }
+    if (ranges_overlap(addr, len, ICH9_LPC_GEN_PMCON_1, 8)) {
+        ich9_lpc_pmcon_update(lpc);
+    }
 }
 
 static void ich9_lpc_reset(DeviceState *qdev)
diff --git a/include/hw/acpi/ich9.h b/include/hw/acpi/ich9.h
index c2d3dba..77cc65c 100644
--- a/include/hw/acpi/ich9.h
+++ b/include/hw/acpi/ich9.h
@@ -39,6 +39,7 @@
     MemoryRegion io_smi;
 
     uint32_t smi_en;
+    uint32_t smi_en_wmask;
     uint32_t smi_sts;
 
     qemu_irq irq;      /* SCI */
diff --git a/include/hw/i386/ich9.h b/include/hw/i386/ich9.h
index f4e522c..a2cc15c 100644
--- a/include/hw/i386/ich9.h
+++ b/include/hw/i386/ich9.h
@@ -152,6 +152,12 @@
 #define ICH9_LPC_PIRQ_ROUT_MASK                 Q35_MASK(8, 3, 0)
 #define ICH9_LPC_PIRQ_ROUT_DEFAULT              0x80
 
+#define ICH9_LPC_GEN_PMCON_1                    0xa0
+#define ICH9_LPC_GEN_PMCON_1_SMI_LOCK           (1 << 4)
+#define ICH9_LPC_GEN_PMCON_2                    0xa2
+#define ICH9_LPC_GEN_PMCON_3                    0xa4
+#define ICH9_LPC_GEN_PMCON_LOCK                 0xa6
+
 #define ICH9_LPC_RCBA                           0xf0
 #define ICH9_LPC_RCBA_BA_MASK                   Q35_MASK(32, 31, 14)
 #define ICH9_LPC_RCBA_EN                        0x1